Waste oil finds its way into the environment through engine use, spills, leaks from exhaust systems and indiscriminate disposal. This study aimed at phytoremediation of spent engine oil (SEO) contaminated soil by using Gmelina arborea seedlings. Pollution was simulated by using four SEOconcentrations:0 ml (Control), 30 ml (T1), 150 ml (T2, and 750 ml (T3) to contaminate vegetated (VG)and unvegetated (UVG) soils. Using 2 × 4 factorial completely randomized design of 15 replicates, data were collected at 57 and 163 days after planting (DAP), and subjected to analysis of variance using SPSS version 23.Mean concentrations of heavy metals in VG soil decreased significantly (Pb: 0.031;Zn:1400; Cu:0.8; Cd: 0.011; Al:4.7 mg/100g) compared to the significant increase in UVG(Pb: 0.046; Zn:1787.5; Cu:2.8; Cd:0.042; Al:5.05mg/100g) soil and showed variation in the mean accumulation in the plant tissues. Pb (0.08), Al (6.88), Cu (0.83) and Cd (0.02) produced highest accumulation in the T3 root, Zn was highest (3,200mg/100g) in the T2 leaves while stem had least accumulations at higher concentrations. Results showed low adverse effects on the plant morphological characterizations but stomatal width and chlorophyll contents of the leaves had variations. Based on the results, G. arborea had a higher tolerance for SEO pollution. Therefore, the plant’s ability to germinate, grow, survive in polluted soil and build-up of heavy metals showed its potency as hyperaccumulator and usefulness as a phytoremediator.
Osayi et al. (Sun,) studied this question.